The background of the invention will be discussed in two parts.
1. Field of the Invention
This invention relates to vortex flow meters, and more particularly to an improved one-piece vortex flowmeter sensor body.
2. Description of the Prior Art
Vortex meters of current design use the localized fluid pressure fluctuations associated with the vortices produced by the bluff body to detect the vortex shedding frequency. The methods used to sense these pressures vary, but most use either a sealed, fluid-filled diaphragm-type differential pressure sensor, or use strain gages or force sensors to detect the forces caused by these pressures in some element of the bluff body.
In such prior art meters, the flowmeter body is formed in two parts, one part being the meter housing for attachment to fittings in a flow line, with the other part being the bluff body. To receive the bluff body, the housing is drilled with a through hole extending through opposing surfaces thereof, with the holes appropriately machined to accommodate the bluff body in a precise fitting relationship. Retention of the bluff body at one end generally requires a plug member. Upon insertion of the bluff body, to provide sealing, O-rings and the like are employed. Such sealing means are subject to failure.
With the two piece arrangement, the bluff body must be precisely oriented relative to the fluid flow to provide the proper vortex creation and hence precise readings from the sensor to be incorporated therein. Bluff bodies may take the form of a wedge-shaped member with a transversely extending slot and an axial opening for insertion of a sensor with the vane bisecting the dimesion within the slot. Differential pressure then results in flexing of the vane which is then converted to an electrical signal. Thus, the bluff body must be oriented on a true diameter of the conduit within the meter housing, with the wedge shaped leading end positioned in the direction of the axis of the tubular conduit. Furthermore, with the two piece arrangement, due to the discrete boundaries at the junctions of the bluff body within the conduit, hydraulic noise occurs, which noise is reflected in decreased sensitivity of the flowmeter. Such construction is very expensive, given the various parameters under consideration.
In accordance with an aspect of the present invention, it is an object to provide a new and improved one-piece vortex meter body which incorporates the bluff body within the meter housing.